1. Field of the Invention
This invention relates to a composition comprising a nitrogen-containing acrylic copolymer, an amine-modified epoxy compound and a blocked polyisocyanate which can be deposited on a cathode by electrocoating; a cross-linked product obtained from the composition; a coating material comprising the composition; and a method of forming a coating by using the coating material.
2. Description of the Prior Art
The method of depositing a coating substance on the surface of a metallic material to be coated as an electrode by electrophoresis is a so-called electrocoating method and is widely used for coating bodies of automobiles. The electrocoating method is classified into two types, i.e., anodic electrocoating using a material to be coated as an anode and cathodic electrocoating using a material to be coated as a cathode. Of these two the cathodic electrocoating which employs, as a cathode, a metal to be coated has such a great advantage that the metal does not dissolve as an ion. An exemplary composition for cathodic electrocoating which is now employed contains a product obtained by reacting an epoxy compound with a secondary amine to convert the epoxy group to an .alpha.-dialkylamino-.beta.-hydroxyethyl group and a blocked polyisocyanate. In this composition the polyisocyanate is half-blocked with the pendent hydroxyl group of the modified epoxy compound.